While laying siege to an enemy's coastal city, they had a sortie and attacked me. The battle was also raged in the sea outside the city. I ran out of footsoldiers to actually kill all of the fortified defenders, but the naval battle continued until the rounds ran out. Once they did, my naval units were placed on the spot the sortie happened, in the middle of the island, continuing the siege. These units cannot move, and will soon die of trespassing after the war ends.

This is the turn before the naval units arrived to the sortie: auto-save 1069.ctr

This is the turn after the sortie ends: Ming Turn 151.ctr

This is the turn they surrendered: auto-save 1076.ctr